The present invention relates generally to wavelength division multiplexing and, more particularly, to wavelength division multiplexing/demultiplexing devices employing patterned optical components.
Optical communication technology relies on wavelength division multiplexing (WDM) to provide increased bandwidth over existing installed fiber, as well as newly deployed fiber installations. Several technologies exist to provide the technical solution to WDM: array waveguide gratings (AWG""s), fiber Bragg grating based systems, interference filter based systems, Mach-Zehnder interferometric based systems, and diffraction grating based systems, to name a few. Each system has advantages and disadvantages over the others.
Diffraction grating based systems have the advantage of parallelism, which yields higher performance and lower cost for high channel count systems. One drawback to traditional diffraction grating based systems, however, is an insertion loss that rises quickly and monotonically as the source illumination drifts off of the center of the desired communication channel wavelength. That is, traditional diffraction grating based systems invariably suffer from a variation in transmission efficiency across a wavelength channel. This variation in transmission efficiency with wavelength creates deleterious effects on modulated signals. For analog signals it creates harmonic distortion, for digital signals it increases the bit-error-rates at higher modulation bandwidths.
Also, most traditional diffraction grating based systems have an inherently gaussian-shaped passband profile. Such a gaussian-shaped passband profile is generally very narrow with a single peak and steep passband edges. Thus, even when a communication channel drifts off of its center wavelength by only a slight amount, signal coupling with a receiving fiber is often severely detrimentally affected.
At least one attempt has been made to alleviate at least one aspect of the above-described shortcomings. For example, as described by D. Wisely in xe2x80x9cHigh Performance 32 Channel HDWDM Multiplexer with 1 nm Channel Spacing and 0.7 nm Bandwidthxe2x80x9d, SPIE, Vol. 1578, Fiber Networks for Telephony and CATV (1991), a microlens may be employed at the end of an input fiber in a WDM device so as to widen the gaussian-shaped passband profile of the WDM device. That is, by widening the gaussian-shaped passband profile of the WDM device, there is less susceptibility to wavelength drift in communication channels. However, widening the gaussian-shaped passband profile of a WDM device may increase the chances of channel crosstalk. Thus, a tradeoff determination must be made when deciding whether or not to implement the above-described technique.
While no other known attempts have been made to alleviate one or more aspects of the above-described shortcomings, it is presumed that such other attempts, if made, would also require certain tradeoffs to be made. Thus, in view of the foregoing, it would be desirable to provide a WDM device which overcomes the above-described inadequacies and shortcomings with minimal or no tradeoffs in an efficient and cost effective manner.
The primary object of the present invention is to provide wavelength division multiplexing/demultiplexing devices which overcome the above-described inadequacies and shortcomings with minimal or no tradeoffs in an efficient and cost effective manner.
The above-stated primary object, as well as other objects, features, and advantages, of the present invention will become readily apparent to those of ordinary skill in the art from the following summary and detailed descriptions, as well as the appended drawings. While the present invention is described below with reference to preferred embodiment(s), it should be understood that the present invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present invention as disclosed and claimed herein, and with respect to which the present invention could be of significant utility.
According to the present invention, improved wavelength division multiplexing/demultiplexing devices are provided. In the case of an improved wavelength division multiplexing device having a diffraction grating for combining a plurality of monochromatic optical beams into a multiplexed, polychromatic optical beam, the improvement comprises employing a plurality of patterned optical input components corresponding to the plurality of monochromatic optical beams, wherein each of the plurality of patterned optical input components introduces a first patterned phase delay into a corresponding one of the plurality of monochromatic optical beams. The improvement also comprises employing a patterned optical output component for introducing a second patterned phase delay into the multiplexed, polychromatic optical beam, wherein the first patterned phase delay and the second patterned phase delay are added so as to reshape the passband of the improved wavelength division multiplexing device.
In accordance with other aspects of the present invention, the plurality of patterned optical input components comprises a plurality of patterned phase masks, wherein each of the plurality of patterned phase masks introduce the first patterned phase delay into a corresponding one of the plurality of monochromatic optical beams. Each of the plurality of patterned phase masks is preferably formed on/in a corresponding collimating microlens. Alternatively, the plurality of patterned optical input components also comprises a plurality of collimating microlenses, wherein each of the plurality of collimating microlenses collimates a corresponding one of the plurality of monochromatic optical beams. In either case, each corresponding collimating microlens or each of the plurality of collimating microlenses contributes to a widening of the passband of the improved wavelength division multiplexing device.
In accordance with further aspects of the present invention, each of the plurality of patterned phase masks has a periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division multiplexing device is typically a gaussian-shaped passband having a peak, and the periodic phase profile of each patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division multiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division multiplexing device is a gaussian-shaped passband having sideband slopes, and the periodic phase profile of each patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division multiplexing device.
In accordance with still further aspects of the present invention, each of the plurality of patterned phase masks has a non-periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division multiplexing device is a gaussian-shaped passband having a peak, and the non-periodic phase profile of each patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division multiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division multiplexing device is a gaussian-shaped passband having sideband slopes, and the non-periodic phase profile of each patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division multiplexing device.
In accordance with other aspects of the present invention, the patterned optical output component comprises a patterned phase mask for introducing the second patterned phase delay into the multiplexed, polychromatic optical beam. The patterned phase mask is preferably formed on/in a focusing microlens. Alternatively, the patterned optical output component also comprises a focusing microlens for focusing the multiplexed, polychromatic optical beam. In either case, the focusing microlens contributes to a widening of the passband of the improved wavelength division multiplexing device.
In accordance with further aspects of the present invention, the patterned phase mask has a periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division multiplexing device is a gaussian-shaped passband having a peak, and the periodic phase profile of the patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division multiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division multiplexing device is a gaussian-shaped passband having sideband slopes, and the periodic phase profile of the patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division multiplexing device.
In accordance with still further aspects of the present invention, the patterned phase mask has a non-periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division multiplexing device is a gaussian-shaped passband having a peak, and the non-periodic phase profile of the patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division multiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division multiplexing device is a gaussian-shaped passband having sideband slopes, and the non-periodic phase profile of the patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division multiplexing device.
In accordance with other aspects of the present invention, the plurality of patterned optical input components and the patterned optical output component cause either constructive or destructive interference to occur as wavelength varies over the passband of the improved wavelength division multiplexing device when the first patterned phase delay and the second patterned phase delay are added. Also, the plurality of monochromatic optical beams and the multiplexed, polychromatic optical beam are beneficially arranged in input and output arrays, respectively, wherein each of the plurality of patterned optical input components and the patterned optical output component has a patterned phase mask, and wherein each patterned phase mask is oriented at an angle relative to the input and output arrays. Further, at least the plurality of patterned optical input components or the patterned optical output component are beneficially formed adjacent to a plurality of non-patterned optical input components or a non-patterned optical output component, respectively.
In the case of an improved wavelength division demultiplexing device having a diffraction grating for separating a multiplexed, polychromatic optical beam into a plurality of monochromatic optical beams, the improvement comprises employing a patterned optical input component for introducing a first patterned phase delay into the multiplexed, polychromatic optical beam. The improvement also comprises employing a plurality of patterned optical output components corresponding to the plurality of monochromatic optical beams, wherein each of the plurality of patterned optical output components introduces a second patterned phase delay into a corresponding one of the plurality of monochromatic optical beams. The first patterned phase delay and the second patterned phase delay are added so as to reshape the passband of the improved wavelength division demultiplexing device.
In accordance with other aspects of the present invention, the patterned optical input component comprises a patterned phase mask for introducing the first patterned phase delay into the multiplexed, polychromatic optical beam. The patterned phase mask is preferably formed on/in a collimating microlens. Alternatively, the patterned optical output component further comprises a collimating microlens for collimating the multiplexed, polychromatic optical beam. In either case, the collimating microlens contributes to a widening of the passband of the improved wavelength division demultiplexing device.
In accordance with further aspects of the present invention, the patterned phase mask has a periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having a peak, and the periodic phase profile of the patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division demultiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having sideband slopes, and the periodic phase profile of the patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division demultiplexing device.
In accordance with still further aspects of the present invention, the patterned phase mask has a non-periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having a peak, and the non-periodic phase profile of the patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division demultiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having sideband slopes, and the non-periodic phase profile of the patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division demultiplexing device.
In accordance with other aspects of the present invention, the plurality of patterned optical output components comprises a plurality of patterned phase masks, wherein each of the plurality of patterned phase masks introduces the second patterned phase delay into a corresponding one of the plurality of monochromatic optical beams. Each of the plurality of patterned phase masks is preferably formed on/in a corresponding focusing microlens. Alternatively, the plurality of patterned optical output components also comprises a plurality of focusing microlenses, wherein each of the plurality of focusing microlenses focuses a corresponding one of the plurality of monochromatic optical beams. In either case, each corresponding focusing microlens or each of the plurality of focusing microlenses contributes to a widening of the passband of the improved wavelength division demultiplexing device.
In accordance with further aspects of the present invention, each of the plurality of patterned phase masks has a periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having a peak, and the periodic phase profile of each patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division demultiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having sideband slopes, and the periodic phase profile of each patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division demultiplexing device.
In accordance with still further aspects of the present invention, each of the plurality of patterned phase masks has a non-periodic phase profile. A benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having a peak, and the non-periodic phase profile of each patterned phase mask contributes to a flattening of the peak of the gaussian-shaped passband of the improved wavelength division demultiplexing device. Another benefit to this aspect is that the passband of the improved wavelength division demultiplexing device is a gaussian-shaped passband having sideband slopes, and the non-periodic phase profile of each patterned phase mask contributes to a steepening of the sideband slopes of the gaussian-shaped passband of the improved wavelength division demultiplexing device.
In accordance with other aspects of the present invention, the patterned optical input component and the plurality of patterned optical output components cause either constructive or destructive interference to occur as wavelength varies over the passband of the improved wavelength division demultiplexing device when the first patterned phase delay and the second patterned phase delay are added. Also, the multiplexed, polychromatic optical beam and the plurality of monochromatic optical beams are beneficially arranged in input and output arrays, respectively, wherein each of the patterned optical input component and the plurality of patterned optical output components has a patterned phase mask, and wherein each patterned phase mask is oriented at an angle relative to the input and output arrays. Further, at least the patterned optical input component or the plurality of patterned optical output components are formed adjacent to a non-patterned optical input component or a plurality of non-patterned optical output components, respectively.
The present invention will now be described in more detail with reference to exemplary embodiments thereof as shown in the appended drawings.